1. FIELD OF THE INVENTION
This invention relates to methods and apparatus for treating wafer-like articles; and, more particularly, for treating thin, fragile, wafer-like articles, such as semiconductor wafers. Such treatment may include, but is not limited to, cleaning, scrubbing, abrading, grinding, and coating.
Although the invention will be described particularly with reference to an embodiment adapted for scrubbing and cleaning semiconductor wafers, it will be appreciated that the invention is not so limited. For example, the invention may be employed for treating, e.g., scrubbing and cleaning, other thin, fragile articles, such as photolithographic masks.
In the field of semiconductor manufacture, considerable attention has been directed toward reducing manual processing steps by replacing those steps with automatic machinery. Such attention is motivated not only by a desire to reduce cost, but also to improve quality by eliminating such factors as breakage and variation in the degree of treatment from article to article.
2. DESCRIPTION OF THE PRIOR ART
Prior to this invention, some mechanized apparatus has been available for treatments such as scrubbing semiconductor wafers. An early form of such apparatus is disclosed in U.S. Pat. No. 3,585,668 issued June 22, 1971 to R. J. Jaccodine et al. The Jaccodine et al. apparatus includes a substantially horizontally disposed, rotatable holder. Wafers are inserted into pockets in the holder, and rotation of the holder brings one side of the wafers to rotating brushes and detergent and rinsing mechanisms. In such apparatus the wafers are initially loaded and then scrubbed on one side, after which the wafers must be turned over if scrubbing on the other side is desired. It is generally desirable to eliminate such multiple handling.
An improvement over the above-described apparatus is disclosed in U.S. Pat. 3,664,872 issued May 23, 1972 and 3,748,677 issued July 31, 1973 to G. A. Frank et al. The Frank et al. apparatus is adapted for simultaneously scrubbing and cleaning both sides of a semiconductor wafer, inasmuch as the wafers are held in generally open slots in a vertically rotating disc. The disc conveys the wafers between a pair of opposed counter-rotating brushes within a detergent spray. The wafers are held in the disc by pockets formed by ledges overhanging the periphery of each slot.
It is advantageous to eliminate such overhanging ledges to prevent masking of those portions of the wafers which are covered by such ledges to thereby improve the cleaning of the entire surfaces of the wafers. Also, to improve the cleaning of the wafers, it is preferable not to use pockets which can trap cleaning residues and thereby detract from the cleaning of the wafers. Another reason for eliminating such pockets is that they support the wafers, which are fragile, only by small portions of the peripheries and therby subject the wafers to stresses produced by the brushes and by the water and detergent streams.